SquirrelMail is a standards-based webmail package written in PHP. It includes
built-in pure PHP support for the IMAP and SMTP protocols, and all pages render
in pure HTML 4.0 (with no JavaScript required) for maximum compatibility across
browsers. It has very few requirements and is very easy to configure and
install. SquirrelMail has all the functionality you would want from an email
client, including strong MIME support, address books, and folder manipulation.

Project origins

The need arose in our organization for the access of email and address books
from anywhere in the world. Obviously a web interface is ideal for this, given
that the user has access to the Internet. After reviewing several open source
projects we realized that we were going to need to do some fairly major
customizations to get things to be a nice fit for our needs. So the decision was
made to create our own for some of these reasons, and for fun (we really like
PHP). We decided to open source the project to contribute to the community that
has contributed so much to us.More SquirrelMail history

Stability

SquirrelMail is stable enough to use in a production system. It is, in fact,
already used in several production systems around the world, handling thousands
of users per system. There might be some bugs - no project is perfect - but they
are most likely minimal. We test pretty thoroughly before releasing a version
marked as "stable".More about scalability

License

SquirrelMail is licensed under the GNU General Public License (GPL), so there
are no license fees to worry about.More about the license